[fs.op.create.dir.symlk] Fix indentation

Author: Andreas-Krug

source/iostreams.tex

@@ -17611,7 +17611,7 @@
 \begin{itemdecl}
 void filesystem::create_directory_symlink(const path& to, const path& new_symlink);
 void filesystem::create_directory_symlink(const path& to, const path& new_symlink,
-                              error_code& ec) noexcept;
+                                          error_code& ec) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}